Wind generator of the type with automatic power regulation

ABSTRACT

The invention relates to a wind generator of the type with automatic power regulation, comprising at least one propeller having at least two blades ( 21 ), whereby the efficiency of one propeller varies inversely to a variation in the wind energy, from a lower wind speed limit. The torque/speed characteristics of each propeller are determined such that the working point begins to move towards the areas of low aerodynamic efficiency when the wind speed approaches the value at which the generator reaches the maximum, safety-compliant power. The inventive wind generator is characterized in that it also comprises: at least one centrifugal counter weight system ( 24 ) which is arranged such as to reduce the pitch of at least one part of the blades when the speed of rotation is increasing; and at least one system comprising an end stop ( 30 ) and return ( 15 ) or compression ( 25 ) means which mechanically define the initial working pitch and the optimum working pitch up to the nominal speed. According to the invention, one part of the blades is pivot mounted to a shaft ( 23 ), thereby driving the end of at least one return spring ( 15 ) or compression spring ( 25 ) by means of at least one arm or lever ( 22 ) or similar device, said end maintaining the blade in contact with at least one fixed end stop element ( 30 ) defining the initial pitch.

FIELD OF THE INVENTION

Wind energy has been used for a long time by means of rotating sails.Windmills are thus known that are provided with wings or blades,generally four in number; but these mills are mostly usable in countrieswhere the winds are more or less regular and always or nearly alwaysblowing in the same direction.

At the present time, more interest is taken in what are commonly calledwind generators or “wind generators”, devices in which the blades aremetal or made from composite materials and therefore relativelynon-deformable. Perfected wind generators provide suitable efficiencieswith, for example, a tail unit forming a fin and which ensures thekeeping of all the mobile elements (for example blades) parallel withthe direction of the wind, whatever the direction of the wind may be, inthe so-called “feathered” position, in order to present minimalresistance to the wind, or in the position opposite to the featheredposition, and therefore the position perpendicular to the direction ofthe wind, with in this case maximum resistance to the wind. When adriving wheel is used for the correct operation of the blades, certaindevices make provision for withdrawing this driving wheel from the windby presenting it sideways in the case of a storm.

Wind generators, as is known, can be used for various applications:pumping water in agricultural applications, supply of electrical energy,and also the supply of hot water by using the heat produced when brakingthe blades when it is appropriate to slow them down for whatever thereasons may be.

It is important for the correct functioning of wind generators toprovide various types of improvements; in fact on wind generators with asingle blade or with several blades, two for example, as these bladesall have large diameters, the speeds of rotation can be very high andthus generate stresses that are difficult to control. Hence air turbinesare sometimes constructed with a small rotor diameter and with a longaxial length, placed at the “convergent” outlet and which protects themfrom limiting peripheral stresses.

The present invention here relates more particularly to the adequatecontrol of the speed of rotation of the wind generators, particularly inviolent wind, that is to say when the maximum amount of energy is beingretrieved but the tips of the blades become too fast and threaten thesoundness or at least the wear of numerous mechanical parts of the windgenerator assembly. More precisely, the device of the invention relatesto the automatic regulation of the pitch of the propeller of a windgenerator.

BACKGROUND OF THE INVENTION

In the prior art, wind generators include a regulation device driven bythe driving shaft of the propeller (of which a mobile regulation shaftis generally coaxial with the driving shaft (FR-2415211).

In FR-2401331, there is described an automatic device for adjusting thepitch of the driving propeller of a wind generator by means of rollersor rods engaged in grooves forming cams arranged in plates carried byeach of the shafts of the blades. The blades can also be actuated by“eccentrics” driven against the action of springs by flyweights bound inrotation to the wheel. In the literature there are also found meansincorporating “eccentrics” driven by the wind itself (FR 2415211) or bya central device controlled by means of the wheel and whose translationcan be provided for example by means of a watt regulator (FR 2401331) ora screw-bolt system reacting to the difference in speed between that ofthe wheel and that of a motor rotating at a reference speed (FR2313576).

The device according to the invention makes it possible not only tosolve the problem of violent winds but it also makes it possible, bymeans of a large pitch in the absence of wind, to facilitate thestarting of the propeller, this pitch then reducing down to an optimumvalue and then increasing if the wind increases, or even to becomefeathered in the case of gusts.

Basic information on wind generators will furthermore be able to befound in the French patent FR 2.500.077.

Without going into detail, it is recalled briefly that another type ofwind generator, like the one that is the subject of the invention, isdirected towards the wind by a fin; the movement is transmitted to thebase of the wind generator by a universal joint and a shaft which drivesflyweights rubbing on a cylinder.

SUMMARY OF THE INVENTION

The present invention relates to the regulation of power of a windgenerator propeller coupled to a generator by giving the blades of thispropeller (there are at least two blades, for example two or four) aprofile such that the efficiency of this propeller varies inversely withrespect to the variation of the energy of the wind. For this purpose,the torque/speed characteristics of the propeller are determined suchthat the operating point starts to move towards the zones of lowaerodynamic efficiency when the speed of the wind approaches the valuefor which the generator reaches the maximum power compatible with safetyas divulged in the French patent N^(o) 1.553.046.

MORE DETAILED DESCRIPTION

In this patent FR-1553046, the essential part of the regulation isacquired without movement of the blades thus resulting in a greaterstability of the regulation than in the usual variable pitch systemswhich reduce the power by increasing the angle setting; the systemdescribed in the French patent N^(o) 1.553.046 added an importantimprovement by being provided with a system of centrifugal flyweightsarranged in such a way as to reduce the setting angle of a part of theblades when the speed of rotation tends to increase, it being alsoprovided with a system of stops and means of return against these stopswhich mechanically define the initial angle setting and the optimumoperational angle setting up to the nominal speed. Generally the bladeis pivoting about a spindle and drives, by the intermediary for exampleof an arm, the end of a return spring which tends to maintain the bladein contact with a fixed stop which defines the initial angle setting.The French patent N^(o) 1.553.046 describes a certain type of springassembly, an assembly which, whilst being very correct, does not havethe advantages of the present invention, also incorporating a system offlyweights and arms but with an original arrangement of at least onespring.

In general, the blade or a part of that blade, can constitute thecentrifugal flyweight system. It is also possible to envisage mountingthe flyweight at the end of an arm integral with the blade, or part ofblade. The arm bearing the flyweight and the arm for attachment of thespring can then form one and the same bellcrank lever.

A variant provides a blade, or part of blade, integral with a heel-piecearranged to drive the mobile end of a second spring, this end beingretained by a second fixed stop when the blade or part of blade hasrotated through a certain angle. In this case, the first stopcorresponds to an initial angle setting which provides a high startingtorque and the second stop (main stop) corresponds to the optimumoperational angle setting up to the nominal speed. This second springcan be attached to a secondary arm which pivots about the axis ofrotation of the blade. This spring brings this secondary arm intocontact with the first stop. Eventually, this second spring bears by itsfree end against the second fixed stop; the heel-piece is then disposedin such a way as to drive this end directly after the rotation of theblade.

FIGS. 1, 2 and 3 are taken from the French patent N^(o) 1.533.046 andillustrate the techniques that the present invention improves.

FIG. 1 shows a blade element and the components of the forces whichresult from the action of a wind W of angle beta on the blade elementwhose angle setting angle is alpha; dP is the lift proportional to theangle of incidence i which is the difference between beta and alpha; ifthe wind generator is lightly loaded, the low values of dF correspond tolow values of dP, and consequently to low values of i; the variations ofangle setting alpha substantially follow those of the wind angle (beta);the inevitable variations of incidence result in large variations in theforces applied to the blades of propellers, resulting in heavy wear ofthe pitch variation mechanisms.

In FIG. 2, the blade 1 is provided with a pitch variation mechanismconstituted by a bellcrank lever 2 integral with the blade and mountedsuch that it pivots about the axis 3 perpendicular to the axis ofrotation of the blade. At one of the ends of the lever 2, there has beenfixed a flyweight 4 and at the other end there has been attached areturn spring 5. A stop 6 determines the initial angle setting alpha ofthe blade.

In FIG. 3, in addition to the main lever 2, connected to the blade 1 andreturned by the spring 5, there is a second lever 7 mounted on the sameaxis 3 as the lever 2 and returned by a spring 8 into contact with astop 10. On the lever 2, there has been fixed a heel-piece 9 disposed insuch a way as to be able to drive the lever 7 against the action of thespring 8 when the lever 2 has pivoted though a certain angle. Asindicated in FR 1.553.046, the spring 5, rather flexible, is thestarting spring and the stop 6 corresponds to an initial angle settingsufficiently large to ensure a high starting torque. At half-speed theangle setting alpha occurs again corresponding to the main stop 10. Thisangle setting remains constant up to the nominal speed beyond which theangle setting is reduced and the main pre-stressed spring 8 is put underload.

In this French patent N^(o) 1.553.046, the springs used work in tensionand the details of this patent are specifically limited to thesetensions. In the present invention, it has been discovered that it couldbe very advantageous, subject to there being some original devices, touse either at least one system with at least two springs arrangeddifferently from the arrangement in FIGS. 2 and 3 (see FIG. 4) or evenmore advantageously at least one spring working not in tension but incompression (see FIG. 5). But, according to the invention, it can alsobe very advantageous to use a mixed technique combining both the devicesof FIGS. 4 and 5, this mixed technique being illustrated in FIG. 6.

In fact it is appropriate to emphasize that the regulation is alwayscarried out in the condition of aerodynamic stalling, a system in whichthe resultant dR (see FIG. 1) varies very little and the variation inangle setting necessary for this regulation is very small. Because ofthis, various imperatives must be taken into account. In fact, the angledR with the perpendicular to the chord of the profile never exceeds, ina forward direction, a value of about ten degrees such that it sufficesto reduce the angle setting by an angle (alpha+10°) in order to beassured that the driving component becomes negative. The regulation isfinally obtained not by variation of dP but by variation of the angle dRwith the plane of rotation.

In brief, due to the mechanism according to the invention, at least oneflyweight system acts against the return force of the spring or springswhen the speed of rotation tends to increase and causes a reduction ofthe angle setting. Furthermore, the devices according to the inventionmake it possible to provide an initial angle setting that is very muchhigher than alpha in order to ensure a very high starting torque.

Another advantage of the devices according to the invention is toenvisage the regulation, no longer with the totality of the blade, butwith one element only, for example with the ends of the blades which areaerodynamically more active.

The succinctly schematized FIG. 4 shows a first aspect of the invention.It describes a device which comprises at least two blades 11. Each ofthem is integral with a bellcrank lever 12 (or a bellcrank arm or anyequivalent means), each of the bellcrank levers being mounted such thatthey pivot about an axis 13 (the figure here showing a system with twoblades and therefore with two axes) these axes are perpendicular to theaxes of rotation of the blades. At each of the ends of the levers 12 isfixed a flyweight 14 and at the other end of each lever 12 is attached areturn spring 15, each of the springs being attached according to theinvention on the one hand to a flyweight 14 integral with one of theblades and, on the other hand, to the end of a lever 12 integral withanother blade. Thus for example, in FIG. 4 representing a system withtwo blades, comprising two levers, two flyweights and two springs, thetwo springs face each other, each one being attached, on the one hand,to each of the two flyweights which face each other symmetrically withrespect to a plane perpendicular to the two bellcrank levers and each ofthese two springs being attached, on the other hand, to the opposite endof the lever to that which connects the spring to the flyweight, thisend, called opposite, in fact being the end of the lever connected tothe other flyweight. In other words, each spring connects the flyweightattached to a lever to the end of the other lever attached to the otherflyweight.

Moreover, a fixed stop 20 corresponds to each lever, in this casetherefore at least two stops 20 which determine the initial anglesetting alpha of each blade. An arrow F′ is the indication of thedirection of the wind W and the other arrows F indicate the separationof the flyweights, the arrows f indicating the rising of the blades. Thelevers lower by the centrifugal effect applied to the flyweights inrotation under the effect of the wind whilst the springs lengthen andapply tension in the opposite direction on the flyweights, thusmaintaining the correct functioning of the wind generator.

In this case there are therefore at least two blades (preferably twoblades) with direct action of one blade on the other with, furthermore,the following two advantages:

Stabilization and damping on the one hand: there is in fact a minimumamount of vibration and noise due to the direct damping effect of theforce differential on the blades due to the wind differential betweenthe blade in the high position and the blade in the low position and thepassage in front of the mast of the blade in the low position.

Absence on the other hand of linkage and of wearing part, which is aconsiderable advantage in comparison with the devices of the prior art.

FIG. 5 shows a second variant of the invention, namely a devicefunctioning with the help of a spring that is compressed and not undertension.

In FIG. 5, the device according to the invention comprises a set of atleast two blades 21 (preferably two blades), each integral with abellcrank lever 22 (in this case preferably two bellcrank levers 22);each bellcrank lever is connected to a flyweight such as 24. Each ofthese bellcrank levers pivots about an axis 23 perpendicular to theplane of the blades or of the bellcrank levers. According to theinvention, the improvement consists not in using a spring connected onthe one hand to a flyweight and on the other hand to an end of abellcrank lever, a bellcrank lever other than the one which is connectedto the flyweight, but in using a spring functioning “in compression” andnot in tension, this spring being connected at its base to at least twostops 30 and this spring being connected at its top to a fixed nut 26.In this variant of the invention, when the levers lower by centrifugaleffect applied to the flyweights rotating under the effect of the wind,thus driving the ends of the bellcrank levers upwards, the spring iscompressed and applies an action in the opposite direction on theflyweights, thus maintaining the correct functioning of the windgenerator.

The two flyweights, in FIG. 5, separate as indicated in the figure(arrows F) with a rising of the blades (arrows f), the arrows f′indicate the direction of the compression or decompression. The arrow F′indicates the flow of the wind W.

In this case there is therefore angle setting by compressed spring whichin particular furthermore provides two advantages:

On the one hand an effect of stabilization and damping, as a meanposition resulting from the forces applied by all of the blades, and bythe presence of this compressed spring, with a minimum of noise andvibration.

On the other hand, the absence of linkage and wearing part.

It is also possible to add a third non-negligible advantage: theregulation of the speed of rotation is carried out very easily by simplevariation of the initial or “off load” compression of the spring.

FIG. 6 shows what was referred to above as the “mixed technique”. ThisFIG. 6 is identical to FIG. 5, that is to say it is characterized by thepresence of at least one spring 25 operating in compression, but itfurthermore comprises at least two springs 15 identical to those whichare shown in FIG. 4. In this case the invention combines the advantagesof the two FIGS. 4 and 5. The function of the spring 25 is mostly adamping action. The function of the springs 15 is mostly a stabilizationfunction. The combined action of the two types of support results in:

-   A major damping function of the springs such as 15. A major    stabilization function in the average position of adjustment of the    central spring (functioning in compression).

This mixed technique offers increased sensitivity of the regulation byminimization of the stiffness of said central spring.

It will therefore be noted that one of the characteristics of thepresent invention is essentially the fact of having at least one pair ofblades, certain elements of one blade being connected to the elements ofthe other blade. In particular, each spring connects the flyweightattached to a lever to the other end of the other lever attached to theother flyweight as described above. This type of device does not appearin other improvements of wind generators described in particular in DE3115202 or in DE 805388 or in FR-A-2817298.

In these documents, the blades are independent of each other and are notlinked to each other for example by the presence of a return spring ofone blade connected to an element of another blade, or by the presenceof a flyweight being connected to a flyweight of another blade.

1. A wind generator of the type with automatic power regulationcomprising at least two blades of at least one propeller, the efficiencyof a propeller varying inversely with respect to the variation of theenergy of the wind, starting from a lower limit of the speed of thewind, the torque/speed characteristics of each propeller beingdetermined such that the operating point starts to move towards thezones of low aerodynamic efficiencies when the speed of the windapproaches the value for which the generator reaches the maximum powercompatible with safety, the wind generator being characterized in thatit also comprises at least one system of centrifugal flyweights arrangedin such a way as to re-duce the angle setting of at least a part of theblades when the speed of rotation tends to increase, at least one systemof stops and means of return or compression which mechanically definethe initial angle setting and the optimum operational angle set-ting upto the nominal speed, a part of the blades being mounted such that itpivots about an axis thus driving by the intermediary of at least onearm or lever or similar device, the end of at least one re-turn springor of a compression spring, tending to maintain it in contact with atleast one fixed stop defining the initial angle setting, the windgenerator also being characterized in that in each pair of bladeselements of one blade are connected to elements of the other blade. 2.The wind generator as claimed in claim 1 comprising at least two blades,each of them being integral with a bellcrank lever or bellcrank arm orsimilar means, each lever pivoting about an axis substan-tiallyperpendicular to the plane containing said bellcrank lever (or plane ofthe blades) and on the one hand being fixed to a first flyweight and onthe other hand being connected to a first spring, this first spring,functioning in tension, being attached on the one hand to said firstflyweight and on the other hand to the end of another lever itself fixedon the one hand to another flyweight which is different from said firstflyweight and on the other hand to another spring which is differentfrom the first spring and also functioning in tension.
 3. The windgenerator as claimed in claim 2, comprising a pair of two blades, of twolevers, of two fly-weights and of two springs.
 4. The wind generator asclaimed in claim 3, characterized in that the wind generator comprisestwo blades 11, each of them being integral with a bellcrank lever 12,the device thus comprising two bellcrank levers 12, each of thebellcrank levers being mounted pivoting about an axis 13, these two axesbeing perpendicular to the axes of rotation of the blades, each of theends of the levers 12 being fixed to a flyweight 14, the other end ofeach lever 12 being attached to a return spring 15, each of the twosprings being attached on the one hand to a different flyweight 14 andon the other hand to the end of a lever 12, the two springs facing eachother, each one therefore being attached on the one hand to one of thetwo flyweights which face each other symmetrically with respect to aplane perpendicular to the two bellcrank levers and each one of thesetwo springs being attached on the other hand to the opposite end of thelever to that which connects the spring to the flyweight, this end,called the opposite end, in fact being the end of the lever connected tothe other flyweight, each spring thus connecting the flyweight attachedto one lever to the end of the other lever attached to the otherfly-weight, the wind generator furthermore comprising a stop 20corresponding to each lever, that is to say two stops 20, whichdetermine the initial angle set-ting alpha of each blade, F′ being theindication of the direction of the wind W and the other arrows F and findicating the movements of the flyweights and of the bladesrespectively.
 5. The wind generator as claimed in claim 1 comprising aset of at least two blades 21, each integral with a bellcrank lever 22,each bellcrank lever being connected to a flyweight such as 24, each ofthese bellcrank levers pivoting about an axis 23, the wind generatorfurthermore comprising at least one spring functioning in compression,this spring being connected on the one hand at its base to at least twostops disposed at one of the ends of each of the levers and on the otherhand at its top to a fixed nut
 26. 6. The wind generator as claimed inclaim 5, comprising two blades 21, two bellcrank levers 22, twofly-weights 24, each bellcrank lever being connected to one of the twoflyweights 24, each of these bellcrank levers pivoting about an axis 23,the device comprising at least one spring 25 functioning “incompression”, this spring being connected at its base to at least twostops 30 and this spring being connected at its top to a fixed nut 26,the two flyweights separating in the direction of the arrow F, withmovement of the blades in the direction of the arrows f, f′ being thedirection of compression and F′ being the direction of the wind W. 7.The wind generator as claimed in claim 1, comprising a set of at leasttwo blades 21, each one integral with a bellcrank lever 22, eachbellcrank lever being connected to a flyweight such as 24, each of thesebellcrank levers pivoting about an axis 23, the wind generator beingcharacterized on the one hand in that it comprises at least one springfunctioning in compression, this spring being connected on the one handat its base to at least two stops disposed at one of the ends of each ofthe levers 22 and on the other hand at its top to a fixed nut 26, thewind generator being characterized on the other hand in that itcomprises at least two other springs 15, called return springs,functioning in tension and each one being attached on the one hand to aflyweight and on the other hand to an end of a bellcrank lever with anarrangement such that each of the ends of the levers 22 is fixed to aflyweight 24, the other end of each lever 22 being attached to one ofsaid return springs 15, each of the two springs being attached on theone hand to a different flyweight 24 and on the other hand to the end ofa lever 22, the two springs facing each other, each one therefore beingattached on the one hand to one of the two flyweights which face eachother symmetrically with respect to a plane perpendicular to the twobellcrank levers and each one of these two springs being attached on theother hand to the opposite end of the lever to that which connects thespring to the flyweight, this end, called the opposite end, in factbeing the end of the lever connected to the other flyweight, each springthus connecting the flyweight attached to one lever to the end of theother lever attached to the other fly-weight, the wind generatorfurthermore comprising at least one stop 30 corresponding to each lever,which determine the initial angle setting alpha of each blade, the arrowF′ being the indication of the direction of the wind W and the otherarrows F and f indicating the movements of the flyweights and of theblades respectively.
 8. The wind generator as claimed in claim 7,comprising two blades 21, two bellcrank levers 22, two fly-weights 24,two axes 23 and two stops 30, each bell-crank lever 22 being connectedto one of the two flyweights 24, each of these bellcrank levers pivotingabout one of said axes 23, the wind generator comprising at least onespring 25 functioning “in compression”, this spring being connected atits base to at least the two stops 30 and this spring being connected atits top to a fixed nut 26, the two flyweights separating in thedirection of the arrow F, with movement of the blades in the directionof the arrows f, the wind generator also comprising two return springs15, each of them being fixed on the one hand to the end of one of thetwo levers 23 and on the other hand to a flyweight 24 attached to theother lever.